This invention relates to joints or couplings, and particularly to a wide-band compression coupling such as used to make connections in a diesel truck exhaust system between the engine exhaust pipe and the flexible metal hose exhaust stack.
In many installations of flexible hose, tubing and piping, it is desirable to install a completely sealed clamp-type coupling to join together the ends of the hose, tube or pipe sections, which may be of the same or different diameters. Such a coupling should be strong, easily installed, and removable to facilitate repair and replacement. These couplings usually have a wide annular sleeve assembly extending circumferentially around the end portion of the tubes or pipes. The sleeve assembly is circumferentially extensible so that the diameter of the sleeve assembly can be increased and the coupling loosened when fitting the coupling around the joint. The coupling also usually has clamping means for tightening and compressing the extensible sleeve assembly around the tube or pipe end once the coupling is in place. The compressive force holds the clamp in place and keeps the ends of the tube or pipe section together.
In U.S. Pat. No. 4,049,298, the present inventor has disclosed a compression coupling of this type having a jacket member with an axially extending wrinkle formed therein directly over the gap formed in the circumferentially extensible sleeve. A sealant could be placed within the wrinkle. As the jacket member was tightened by the clamping means, the wrinkle flattened, forcing the sealant down into the gap. The clamping means disclosed in the aforementioned patent comprised a pair of bars, one attached to the jacket member and the other attached to a flange connected to the sleeve. The bars were provided with holes through which bolts were inserted, with nuts threaded along the bolts to provide a suitable fastening means. The circumferential tightening movement or displacement of the jacket member was provided solely by the displacement of the nut along the threaded portion of the bolt. Thus, in order to displace the end of the jacket member a distance of two inches, it was necessary for the nut to travel two inches along the shank of the bolt. Since it is necessary to alternate tightening the two bolts, the clamping means required considerable installation time during which the installer performed the necessary operation to alternatively tighten the bolts.
Another disadvantage with the clamping means of the aforementioned Foti patent was that the bars were relatively unsupported during the clamping operation. Unless both bolts are tightened substantially simultaneously, the bars would tend to bend as a result of the larger compressive force being exerted at one end of the bar than the other. In order to balance the force during the clamping operation, it was necessary to successively alternate between tightening one bolt and the other. This requirement made the clamping operation extremely cumbersome and time-consuming since it was necessary to alternate between the bolts numerous times.
Other clamping means have been disclosed, such as that shown in U.S. Pat. No. 3,905,623 issued to P. R. Cassel. Cassel discloses a wide-band clamp-type coupling for placing around the adjacent ends of tubing having the same outer diameters. The clamping means for this coupling comprises a pair of rounded spacer bars on each side of an inwardly opening radially extending channel formed in the sleeve which extends around the tubing. An anvil-shaped spline is positioned within the channel. As the bolts are tightened, the sleeve conforms to the shape of the spline, thereby drawing the sleeve tighter around the pipe. When the bolts are fully tightened and the sleeve is securely compressed against the spline, the spline forms part of the seal along the tubing connection.
A major disadvantage with the wide-band coupling disclosed in the Cassel patent is that its utility is limited to tubing of a fixed equal outer diameter. The ability to accommodate tubing with a range of outer diameters is important since tubing of a specific size may not always be available. With Cassel's coupling it is not possible to accommodate tubing of various outer diameters within a certain range because the sleeve must be fully tightened in a fixed position to form the seal. If the bolts are not fully tightened, a complete seal is not formed, and after fully tightening the bolts further tightening is impossible because the center spline acts as a stop to limit further motion of the spacer bars.
It is also not possible to use Cassel's wide-band coupling of connections between tubing having unequal outer diameters. The capability of joining ends of tubing having different outer diameters is important, for example, in making the connection between the diesel truck engine exhaust pipe and the flexible metal hose exhaust stack having the same inner diameters, because the flexible metal hose of the same inner diameter as the metal hose is made of a heavier material and has a thicker wall, resulting in a greater outer diameter. To use Cassel's coupling it is necessary to use a flexible hose of a smaller size, resulting in uneven inner diameters. Since standard hose is designated and ordered by its inner diameter measurement a special diameter hose must be used with Cassel's coupling to achieve equal outer diameters between the hose and the pipe.
Another disadvantage with Cassel's coupling is that it cannot be removed simply by loosening the bolts. Once the sleeve has been deformed into the concave sides of the center spline, the sleeve will remain taut around the tubing even after the bolts have been loosened and the spacer bars have been removed. The sleeve cannot be readily deformed back to its original shape. To remove Cassel's coupling, the tubing thus must be burned apart on each side of the coupling. As a result, about 11/2 inches of tubing on each side of the coupling will be lost each time the coupling is replaced.
In the aforementioned Cassel patent, a coupling is also disclosed in which the adjacent ends of the tubing are deformed, and one tubing end is inserted inside the other. The clamping means again comprises a pair of rounded spacer bars, and the center spline is provided by an anvil shape in the deformed inner tubing. A center reinforcing member is added to this anvil-shaped portion of the inner tubing. As with Cassel's wide band coupling, this coupling is limited to tubing of a certain outer diameter and will not accommodate a range of outer diameters. Furthermore, this coupling requires special tubing having ends specially deformed to interfit and to accommodate the clamping means.
The capabilities of all of these prior art clamping means was limited because the amount of displacement which could be performed on the sleeve assembly was limited. In the prior Foti patent the displacement was limited by the length of the shank of the bolt which attached the two bars. In the prior Cassel patent the displacement was limited by the amount of deformation performed by the spacer bars which engage the inner spline.